OCD about the Talar Dome
Author: Katie Dolbec, MD, CAQ-SM
Peer-reviewer: Terese Whipple, MD, CAQ-SM
Final editor: Alex Tomesch, MD, CAQ-SM
A patient presents to the Emergency Department with difficulty bearing weight on the right lower extremity after sustaining an inversion injury to the right ankle just prior to presentation. On exam she has moderate right ankle swelling. She is tender over the anterior joint line, particularly laterally. There is no bony tenderness of the malleoli, the calcaneus, the navicular, or the 5th metatarsal. There is no tenderness over the Lisfranc joint. She is tender over the anterior talofibular ligament (ATFL) and the calcaneofibular ligament (CFL). No tenderness with tib-fib compression testing. Right ankle x-rays are obtained (Image 1).
Image 1. Images are the author’s own.
What is your diagnosis?
Talar dome fracture, likely osteochondral defect
At first glance, this is a straight-forward lateral low-ankle sprain. She is tender over the lateral ligaments (ATFL and CFL). And the x-rays appear to be negative for acute fracture or dislocation. But are they really? On closer look, there is an avulsed bony fragment over the superior lateral talar dome, seen best on the AP and mortise projections (Image 2).
Image 2. Same images as previous with annotation
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Pearl: Look closely at the entirety of the talar dome when (independently!) reviewing ankle x-rays after an inversion injury.
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Pearl: Although not visible on plain radiographs, there is articular cartilage covering the entirety of the articular talar dome. The small bony fragment also contains a chunk of the articular cartilage.
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Pearl: The fractured piece of bone and cartilage, termed an osteochondral defect (OCD), is at risk for non-union and eventual displacement from the talar dome and into the joint space, constituting a bothersome and destructive intra-articular loose body.
References:
[1] Zanon G, DI Vico G, Marullo M. Osteochondritis dissecans of the talus. Joints. 2014;2(3):115-123. Published 2014 Aug 1. doi:10.11138/jts/2014.2.3.115